package 数据库的增删改查.课后练习;

import org.junit.Test;
import 数据库的增删改查.util.JDBCUtils;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.util.Scanner;

/**
 * @ClassName Exer2Test
 * @Description TODO
 * @Author lmy
 * @Date 2022/3/15 20:41
 **/
public class Exer2Test {
    /*问题1 向examstudent表中添加一条记录
    Type:
    IDCard:
    ExamCard:
    StudentName:
    Location:
    Grade:
     */
    @Test
    public void testInsert() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入四级/六级");
        int type = scanner.nextInt();
        System.out.println("请输入身份证号:");
        String IDCard = scanner.next();
        System.out.println("请输入准考证号:");
        String ExamCard = scanner.next();
        System.out.println("请输入学生姓名");
        String StudentName = scanner.next();
        System.out.println("请输入所在城市:");
        String Location = scanner.next();
        System.out.println("请输入考试成绩");
        int Grade = scanner.nextInt();

        String sql = "insert into examstudent(type,IDCard,ExamCard,StudentName,Location,Grade)values(?,?,?,?,?,?)";
        int insertCount = update(sql, type, IDCard, ExamCard, StudentName, Location, Grade);
        if (insertCount > 0) {
            System.out.println("添加成功");
        } else {
            System.out.println("添加失败");
        }
    }

    // 通用的增删改操作
    public int update(String sql, Object... args) {// sql中占位符的个数与可变形参的长度相同！
        Connection conn = null;
        PreparedStatement ps = null;
        try {
            // 1.获取数据库的连接
            conn = JDBCUtils.getConnection();
            // 2.预编译sql语句，返回PreparedStatement的实例
            ps = conn.prepareStatement(sql);
            // 3.填充占位符
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i + 1, args[i]);// 小心参数声明错误！！
            }
            // 4.执行
            /*
             * ps.execute():
             * 如果执行的是查询操作，有返回结果，则此方法返回true;
             * 如果执行的是增、删、改操作，没有返回结果，则此方法返回false.
             */
            //方式一：
//			return ps.execute();
            //方式二：
            return ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 5.资源的关闭
            JDBCUtils.closeResource(conn, ps);

        }
        return 0;
    }
    //问题2：根据身份证号或者准考证号查询学生成绩信息
    @Test
    public void queryWithIDCardOrExamCard() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入您要输入的类型:");
        System.out.println("a.准考证号");
        System.out.println("b.身份证号");
        String selection = scanner.next();
        if ("a".equalsIgnoreCase(selection))   //(selection.equalsIgnoreCase("a"))
        {
            System.out.println("请输入准考证号：");
            String examCard = scanner.next();
            String sql = "select FlowID flowID,Type type,IDCard,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where examCard = ?";

            Student student = getInstance(Student.class,sql,examCard);
            if(student != null){
                System.out.println(student);
            }else{
                System.out.println("输入的准考证号有误！");
            }
        } else if ("b".equalsIgnoreCase(selection))
        {
            System.out.println("请输入身份证号：");
            String IDCard = scanner.next();
            String sql = "select FlowID flowID,Type type,IDCard,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where IDCard = ?";

            Student student = getInstance(Student.class,sql,IDCard);
            if(student != null){
                System.out.println(student);

            }else{
                System.out.println("输入的身份证号有误！");
            }
        }else {
            System.out.println("您的输入有误,请重新进入程序!");
        }
    }
    /**
     *
     * @Description 针对于不同的表的通用的查询操作，返回表中的一条记录
     * @author shkstart
     * @date 上午11:42:23
     * @param clazz
     * @param sql
     * @param args
     * @return
     */
    public <T> T getInstance(Class<T> clazz,String sql, Object... args) {
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            conn = JDBCUtils.getConnection();

            ps = conn.prepareStatement(sql);
            for (int i = 0; i < args.length; i++) {
                ps.setObject(i + 1, args[i]);
            }

            rs = ps.executeQuery();
            // 获取结果集的元数据 :ResultSetMetaData
            ResultSetMetaData rsmd = rs.getMetaData();
            // 通过ResultSetMetaData获取结果集中的列数
            int columnCount = rsmd.getColumnCount();

            if (rs.next()) {
                T t = clazz.newInstance();
                // 处理结果集一行数据中的每一个列
                for (int i = 0; i < columnCount; i++) {
                    // 获取列值
                    Object columValue = rs.getObject(i + 1);

                    // 获取每个列的列名
                    // String columnName = rsmd.getColumnName(i + 1);
                    String columnLabel = rsmd.getColumnLabel(i + 1);

                    // 给t对象指定的columnName属性，赋值为columValue：通过反射
                    Field field = clazz.getDeclaredField(columnLabel);
                    field.setAccessible(true);
                    field.set(t, columValue);
                }
                return t;
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.closeResource(conn, ps, rs);

        }

        return null;
    }

    //问题3：删除指定的学生信息
    @Test
    public void testDeleteByExamCard(){
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入学生的考号:");
        String examCard = scanner.next();
        //查询指定准考证号的学生
        String sql = "select FlowID flowID,Type type,IDCard,ExamCard examCard,StudentName name,Location location,Grade grade from examstudent where examCard = ?";
        Student student = getInstance(Student.class,sql,examCard);
        if(student == null){
            System.out.println("查无此人，请重新输入");
        }else{
            String sql1 = "delete from examstudent where examCard = ?";
            int deleteCount = update(sql1, examCard);
            if(deleteCount > 0){
                System.out.println("删除成功");
            }
        }
    }

    //优化以后的操作：
    @Test
    public void testDeleteByExamCard1(){
        System.out.println("请输入学生的考号:");
        Scanner scanner=new Scanner(System.in);
        String examCard=scanner.next();
        String sql="delete from examstudent where examCard=?";
        int deleteCount = update(sql, examCard);
        if (deleteCount>0)
        {
            System.out.println("删除成功");
        }else{
            System.out.println("查无此人,请重新输入");
        }
    }
}
